As we knew, the French defender was not wholly Porto's property. The release to the CMVM confirmed the sale of their 57.67 percent for an eye-watering €30.5 million (£24.3 million). Regarding the rest of the economic rights to Mangala, 33.3 percent was owned by Doyen Sports (more on them later) and 10 percent by a company called Robi Plus, a London-based company linked to agent (and former Standard vice president) Luciano D'Onofrio in a report by television network France 2 in October.

Aligning an agreement among numerous parties, rather than just the traditional two, can take time. So far, so normal in the life of a Portuguese transfer. The sticky issue of third-party ownership may not be to the tastes of the Premier League -- or indeed something that is permitted once players are here -- but it can't be avoided and is unlikely to disappear.

Mangala's move to Man City once again raises awareness for third-party transfers.

Third-party ownership had already delayed the completion of Lazar Markovic's transfer from Benfica to Liverpool earlier this summer, with the Liga champions having only purchased half of the Serbian midfielder's transfer rights when signing him from Partizan Belgrade last summer. The rest belonged to a group of investors "with links to [super-agent] Pini Zahavi," as Portuguese daily newspaper Diario de Noticias put it at the time of the deal. Incidentally, Benfica all but doubled their money, having paid Partizan €6 million before selling to Brendan Rodgers' side at the €25 million buyout clause.

The aftermath of the infamous Carlos Tevez and Javier Mascherano affair, and the closing of a loophole exploited when the pair joined West Ham in August 2006, had apparently put a stop to English involvement in the practice. Their unlikely joint transfer had its roots in Kia Joorabchian's involvement with the takeover of Brazilian giants Corinthians by Media Sports Investments (MSI) in 2004, fronted by the Iranian-born businessman.

The pair's "parking" at West Ham may have seemed an unusual choice but it made perfect economic sense. The most money to be made was (and still is) in transfers between English clubs, so that was the place to get them to, even if the Hammers' rights over the players were notional at best.

The controversial moves of Tevez and Mascherano's to West Ham began England's distrust of third-party deals.

With the cash involved in the Premier League these days, it's natural that third-party investors would be keen to sell their interests to England, even if the possibility of retaining that interest and augmenting it during movement within the league itself is no longer possible since the rule changes.

Uber-agent Jorge Mendes -- the representative of Mangala, Jose Mourinho, Radamel Falcao and pretty much anyone of note who has passed through Portuguese football -- and former Chelsea chief executive Peter Kenyon acknowledged as much when they were setting up a player investment fund, Quality Sports Investments, in 2011. Their prospectus, pitched to wealthy potential investors, pointed out the sums that could be -- and had been -- made especially through moving players from Portugal to England, citing the examples of Manchester United's Anderson and Ramires of Chelsea.

It was a self-fulfilling prophecy. When Diego Costa completed his move to Stamford Bridge this summer, Atletico Madrid banked just half of the €38 million fee specified in the Spain striker's release clause. Other happy parties were Mendes (who owned 10 percent), Costa's old club Braga (20 percent) and Quality Sports Investments itself, who owned the rest, raking in a cool €7.6 million.

Costa's move to Chelsea didn't just benefit Atletico Madrid, but three other entities.

Portugal may be Europe's hotbed of third-party ownership, partly because of its longstanding links with South America's transfer market, but in this era of polarisation between the haves and have-nots, it is widespread. Atletico and Sevilla are among the clubs to have been heavily subsidised by Doyen Sports.

Sevilla's dealings are an example of how the price of liquidity can be a loss of liberty. When they signed Geoffrey Kondogbia in summer 2012, Doyen went halves with the financially strapped Andalucians on a modest €3 million fee. They were lucky that Monaco became interested last year, eventually paying the France midfielder's full €20 million release clause, and that Doyen believed they could play hardball.

The original sale contract stipulated that in the case of a written offer of at least €6 million for Kondogbia, Sevilla either had to sell their half or buy out Doyen's 50 percent stake. The Europa League winners had hoped to snare another Doyen client, Twente's Dusan Tadic, this summer to replace Barcelona-bound Ivan Rakitic before Southampton's straight cash offer blew their bid out of the water.

Yet the Premier League's money can't smooth all the bumps in the road. The Saints' recently rejected €17 million offer for Sporting Lisbon's Marcos Rojo, as reported by Saturday's O Jogo, is a case in point. Sporting only own 25 percent of his transfer rights, while 20 percent of any transfer profit must be paid to his previous club, Spartak Moscow. If Rojo was sold for €20 million, €3.2 million would go the Russian Premier League side (from whom the Argentinian was signed for €4 million), leaving Sporting with just €4.45 million of the remaining amount.

In a hand-to-mouth football economy like Portugal's, it's not difficult to see the immediate advantages. Last season's Liga title race always looked like it might hinge on the January transfer window. Benfica were clearly the superior side in the division, but how would they survive the sales?

Benfica profited from third-party ownership in 2013-14, winning three trophies and making money.

On deadline day came the answer to their prayers. A player investment fund, Meriton Capital Limited, purchased the rights to forward Rodrigo and young midfielder Andre Gomes for a total of €45 million. The Portuguese champions would be due up to €10 million more for Rodrigo depending on performance-related objectives, and 25 percent of any future profit made on Gomes. In the short term, they banked the money and kept the players, winning three trophies. Now, with the pair gone to Valencia -- owned by Meriton investor Peter Lim -- they're picking up the tab.

So Mangala is the tip of the iceberg. In an ideal world, third-party ownership wouldn't happen but today, it's an increasingly well-used way of surviving. Lawyers of Premier League clubs can prepare themselves for complicated deals aplenty.

Andy Brassell is a freelance European football writer and broadcaster for the BBC, The Independent, ESPN, The Blizzard, Four Four Two, Talksport and others.